This message informs all windows that the window with input focus has realized its logical palette, thereby changing the system palette. This message allows windows without input focus that use a color palette to realize their logical palettes and update their client areas.
wParam
Contains the handle of the window that caused the system palette to change.
lParam
This parameter is not used.
To avoid creating a loop, a window that receives this message should not realize its palette unless it determines that wParam does not contain its window handle.